Several dozen environmental activists scaled Britain's Parliament building Sunday to draw attention to climate change.

Greenpeace said 55 of its members were atop the building with yellow banners reading "Change the politics, save the climate."

It said the protesters scaled the neo-Gothic, 19th-century landmark using ladders and ropes.

The Metropolitan Police said officers were speaking to the protesters and there had been no arrests yet. The force said it thought there were 20 or 30 people on the roof of Parliament's Westminster Hall.

The group said it planned to stay overnight so it could welcome lawmakers, who return from their summer break on Monday.

"We are here to remind them that they simply haven't done enough to stop climate change and we need to see some action at home," protester Anna Jones, 28, said via a cell phone from the rooftop.

The demonstrators want legislators to sign a 12-point climate manifesto calling for steep cuts in carbon emissions and investment in renewable energy.

Britain has vowed to reduce its carbon emission by 34 percent in 2020 from 1990 levels.

On Monday, Parliament's Climate Change Committee is due to issue a report assessing how the government is doing on reducing emissions, meeting carbon budgets and building a low-carbon economy.

Security in the Houses of Parliament — home to both the House of Commons and House of Lords — has been tightened following a spate of intrusions in recent years.

A group of climate-change activists managed to sneak onto the roof last year. In 2004, Otis Ferry, son of rock star Bryan Ferry, and seven other men stormed the Commons chamber in 2004 in a pro-fox hunting protest. Months earlier, fathers' rights campaigners hurled purple powder at then-Prime Minister Tony Blair from the public gallery.